Sliding doors have been used for many years to secure various enclosures, including those for cold storage facilities in manufacturing plants, warehouses, garages, and other industrial rooms.
Others have developed track systems and drive systems which operate together to open and close single panel and multi-panel sliding doors. For example, U.S. Pat. No. 1,054,376 to Weidrich discloses a sliding door hanger and track. In Weidrich a rotating wheel, similar to a pulley, rides along a track with the door being suspended from the axle of the wheel. The door can be slid manually along the track from an opened to a closed position, and vice versa. Subsequent to Weidrich, U.S. Pat. No. 4,344,206 to Hermanson discloses a channel track system which supports a sliding door from the axle of two transversely mounted wheels. Other examples of this “track and wheel” configuration are shown in U.S. Pat. Nos. 4,619,075 to Wiles; 4,651,469 to Ngian et al; 4,680,828 to Cook et al.; 4,770,224 to Dubbelman; and 4,819,743 to Rousselot et al.
An area which has not received much attention in this field is the ability to preserve the seals on the door panel during actuation of such doors. In the use of bi-parting doors, either sliding or folding, the bottom seal of such doors often slide along the bottom of the doorway during operation. Such sliding often results in frictional abrasion and wear on the bottom seal of the door. Such wear can often result in heat loss, cold loss. The sliding operation may also increase and wear on other parts of the door assembly as a result of vibrational noise. Such wear on the bottom seal and the door assembly generally can also result in extended down time and increased replacement costs.
Systems such as those disclosed in U.S. Pat. No. 6,330,763 to Kern et al. have been developed in an attempt to address some of the issues described above. However, there still exists limitations inherent to such systems. For example, the system described in U.S. Pat. No. 6,330,763 utilizes angled track and attempts to reduce wear on the lower seal by tilting the panels away from the floor as the door moves toward the closed position or as it just begins to open. The system disclosed in U.S. Pat. No. 6,330,763, however, has some inherent drawbacks. For example, the use of an angled track may cause tumultuous movement of the door as it moves toward its closed position and one portion of the door panel makes contact with the bottom of the opening before the trailing edge comes to rest on the bottom surface. This unsynchronized contact may cause damage, not only to the door seals, but also to the other components of the door assembly. Moreover, the system described in U.S. Pat. No. 6,330,763 increases the possibility of creating an uneven or deficient seal between the door panel bottom and the bottom of the opening.
The present invention has achieved a more reliable, more durable, and more cost effective system for opening and closing sliding doors, such as those used for warehouses, cold storage, freezers, and the like. Thus, while the systems discussed above have been met with a reasonable degree of success, the present invention is provided to solve the problems discussed above and other problems, and to provide advantages and aspects not provided by prior doors of this type.